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I A. JOHNSON. Screw Propeller.

Patented Dec. 8,1857.

UNITED STATES PATENT OFFICE.

ALMER JOHNSON, OF BUFFALO, NEW YORK.

PROPELLER.

Specification of Letters Patent No. 18,814, dated December 8, 1857.

To all whom it may concern:

Be it known that I, ALMER JOHNSON, of the city of Buffalo, in the countyof Erie and State of New York, have invented certain new and usefulImprovements in Propeller-VVheels; and I do hereby declare that thefollowing is a full and exact description thereof, reference being hadto the annexed drawings, making a part of this specification, in whichFigure I, is a plan view of the front surface of the blade. Fig. II, isa plan view of the rear surface of the blade. Fig. III, is a front,isometrical perspective of the wheel. Fig. IV, is a top plan view of thesame.

The nature of my invention embodies the following distinguishingfeatures: 1st. That part of the blade contiguous to the hub, and whichfor distinction I call the stem, is curved in both surfaces thereof, thecurved lines in the one surface running in the reverse direction to thecurved lines in the other surface. 2d. The stem has an inclinationforward, or in a direction toward the bow of the vessel. 3d. That partof the blade above the stem (and which for distinction I call the fan)elongates laterally from the stem, and presents a plane surface (ornearly so) on both sides thereof (except the necessary bevel to form anedge). tth. The fan bears such relation to the stem that if acircumferential line representing the upper edge of the fan, is letfall, in a direction perpendicular to the axis of the wheel, it willclear the stem.

In constructing my wheel I observe the following rules:

1st. Determine the diameter of the propeller to be constructed, or whichis the same thing the extreme height of the fan above the hub.

2d. Then determine the extreme length of the fan, which also inconnection with the angle upon which it crosses the axis will determinethe lead of the propeller.

3. Strike a line at about two-sixths the distance from the hub to theextreme height of the fan. This line indicates the division between thestem and the fan.

4th. Let the base of the stem, as it sits upon the hub, cross the axisonan acute angle. The required lead of the propeller, and the length ofthe fan, will determine the degree of this angle.

5th. Give the stem a sufficient inclination forward, and let the fanbear such relation thereto, so that if a circumferential linerepresenting the upper edge of the fan, is let fall, in a directionperpendicular to the axis, it will fall outside of the stem.

6th. Let the front and rear surfaces of the stem be'curved in oppositedirections, that is to say, let the curved lines on the front surfacedescribe a gradually increasing curved surface from front to rear, andlet the curved lines on the rear surface describe a gradually increasingcurved surface from rear to front. 1!

7th. Make both surfaces of the fan plane, (or nearly so,) exceptthenecessary bevel to form an edge.

The line L (Figs. I, II, and III,) indicates the division between thestem and fan.

The arrow, (Figs. I and II) indicates the entering edge of thepropeller.

The arrow 2 (Fig. IV,) indicates the direction in which the wheelrevolves.

The lines 1, 2, 3, &c. (Figs. I and II,) indicate the direction whichthe curves take on each surface of the stem.

The line M (Fig. IV) indicates the circumferential line of the fan whichfalls outside of the stem.

By observing the rules herein given, and the application of ordinaryskill belonging to the art, propellers, including my invention, may beconstructed of any required diameter or lead.

Among the advantages I claim for my improvement over propellers incommon use are: let. The propeller encounters less resistance in itsmovement through the water, by reason of the increased room or spaceobtained between the blades. 2d. The action of the water upon both sidesof the stem instead of retarding has the the effect to .propel thewheel. 3d. As soon as the inertia of the water is moved, the fan letsgo, that is to say the fan does not hold or carry the water after itsinertia has been disturbed. The entire surface of the stem and fan has apropelling effect.

Constructing propellers which embody the distinctive features of myinvention substantially as herein set forth.

ALMER J OHNSO Witnesses:

E. B. FORBUSH, W. H. FoRBUsH.

